Just to explain the reason there is a login at all, this is mostly for historical reasons. The original learnnextjs.com built by Arunoda was based on another project he created for teaching Meteor.
Anyway as said we're rewriting /learn, using MDX (http://github.com/mdx-js/mdx) for content and the quizzes will store the result in your browser.
Thank you for providing feedback in a friendly way, we're always happy to improve where possible! In case you're curious we have a WIP pull-request: https://github.com/zeit/next-site/pull/159
If you don't like Next or don't see its usefulness thats fine, but 30,000 stars on Github and pretty varied list[1] of companies seems to suggest that some people do find it useful.
I am not affiliated with Zeit or Next.js in any particular way. Just a happy user of Next and appreciative of all the hard work put into it.